Characterization of choline kinase in human endothelial cells

High choline kinase‐α (Chk‐α) expression is frequently observed in cancer cells, making it a novel target for pharmacological and molecular inhibition. As inhibiting agents are delivered systemically, it is important to determine Chk‐α expression levels in endothelial cells that line both normal and tumor vasculature, and the effect of Chk‐α downregulation on these cells. Here, we characterized Chk‐α expression and the effect of its downregulation in human umbilical vein endothelial cells (HUVECs) relative to MDA‐MB‐231 human breast cancer cells. We used small interfering RNA (siRNA) to downregulate Chk‐α expression. Basal mRNA levels of Chk‐α were approximately three‐fold lower in HUVECs relative to MDA‐MB‐231 breast cancer cells. Consistent with the differences in Chk‐α protein levels, phosphocholine levels were approximately 10‐fold lower in HUVECs relative to MDA‐MB‐231 cells. Transient transfection with siRNA‐Chk resulted in comparable levels of mRNA and protein in MDA‐MB‐231 breast cancer cells and HUVECs. However, there was a significant reduction in proliferation in MDA‐MB‐231 cells, but not in HUVECs. No significant difference in CD31 immunostaining was observed in tumor sections obtained from mice injected with control luciferase‐short hairpin (sh)RNA or Chk‐shRNA lentivirus. These data suggest that systemically delivered agents that downregulate Chk‐α in tumors will not affect endothelial cell proliferation during delivery, and further support the development of Chk‐α downregulation as a cancer‐specific treatment. Copyright © 2013 John Wiley & Sons, Ltd.